Various cable hoist devices have been developed over the years which incorporate a plurality of telescopically arranged masts which are capable of being elevated to substantial heights for lifting loads. One such such extensible hoist is set forth in U.S. Pat. No. 3,337,187 of J.D. Sumner. Another three masted cable hoist is set forth in U.S. Pat. No. 4,508,316 of Millard.
Although the present invention is discussed particularly as it relates to three masted cable hoists, it is to be born in mind that such is not intended to limit the scope of the present invention. The present invention is readily applicable to all types of cable hoists that incorporate movable load supporting cable operated carriages that are disposed in movable relation with a mast structure.
Although all cable hoist mechanisms operate for the lifting of loads with the mast structure thereof disposed in upstanding position, certain cable hoists are capable of lying on their sides to render them sufficiently portable so that they may be hauled in small vehicles and efficiently stored and handled in small spaces. Although most cable hoist mechanisms of this nature can readily be positioned on their sides for storage, certain problems exist when these hoists are being transported. Because the hoists incorporate a plurality of masts that are operated by one or more cables for extension and retraction, when the hoist is positioned on its side, the masts can become inadvertently extended, sometimes to the point that the upper masts sections can become completely disassembled from the lower mast section. This becomes a particular hazard from the standpoint of transportation because the vibration of transportation tends to cause inadvertent separation of the mast sections in the event they are not restrained in some fashion. Obviously, when the mast sections become completely separated, the cable can become mispositioned with respect to the sheaves of the mast sections such that reassembly of the hoist becomes very difficult and time consuming. Further, it is possible that the mast sections can become damaged if they should become completely separated during transportation. It is desirable, therefore, to provide a cable hoist mechanism incorporating a facility for positively securing the cable hoist in its collapsed position and to positively insure its inadvertent extension of the mast sections while the hoist is lying on its side during transportation or storage.